Given f(x)={\begin{matrix}(2-\mathrm{sin}(\frac{1}{x}))|x|, & x\neq 0 \\ 0, & x=0\end{matrix} and we know that
|x|={\begin{matrix}x, & x\geq 0 \\ -x, & x<0\end{matrix}
\Rightarrow f(x)={\begin{matrix}-x(2-\mathrm{sin}(\frac{1}{x})), & x<0 \\ 0, & x=0 \\ x(2-\mathrm{sin}(\frac{1}{x})), & x>0\end{matrix}
Now, differentiating using product rule,
\Rightarrow {f}^{'}(x)={\begin{matrix}-(2-\mathrm{sin}\frac{1}{x})-x(-\mathrm{cos}\frac{1}{x}\cdot (-\frac{1}{{x}^{2}})), & x<0 \\ (2-\mathrm{sin}\frac{1}{x})+x(-\mathrm{cos}\frac{1}{x}(-\frac{1}{{x}^{2}})), & x>0\end{matrix}
\Rightarrow {f}^{'}(x)={\begin{matrix}-2+\mathrm{sin}\frac{1}{x}-\frac{1}{x}\mathrm{cos}\frac{1}{x}, & x<0 \\ 2-\mathrm{sin}\frac{1}{x}+\frac{1}{x}\mathrm{cos}\frac{1}{x}, & x>0\end{matrix}
Since f′(x) is an oscillating function and hence it is non-monotonic in (−∞,0)∪(0,∞).